Audible signal device



Feb. 25!, 1936.

M. E. PiPKIN ET AL Zfififi? AUDIBLE SIGNAL DEVICE Filed Jan. 28, 1928 2 Sheets-Sheet l MAU/Z/CE E. P/PK/N ELI JUDSON'BLAKE Feb 25, 1936, M. E. PIPKIN ET AL fi AUDIBLE SIGNAL DEVICE Filed Jan. 28, 1928 I 2 Sheets-Sheet 2 g 72 ms /00 m2 F76. IO. Zl MAUE/CE E. P/PK/N ELI JUDSO/V BLAKE Patented Feb. 25, 1936 2 031,557

UNITED STATES PATENT OFFICE AUDIBIJE SIGN DEVICE MaurjiceE. Pipki'n, New York, and Eli Judson Blake, Rochester, N. Y.; said Blake assignor to said Pipkin Application January 28, 1928, Serial No. 250,238

5 Claims. (01. 177-7) This invention relates to an improvement in Fig. 12 is a diagrammatic view of one type of audible signal devices and more particularly in circuit that might be employed in the embodihorns of the diaphragm type, and the means for ment shown in Fig. 8. producing the vibration'of the diaphragm. The embodiment of this invention selected for Horns of the diaphragm type are old and 11 illustration in Figs. 1 to 4 inclusive of the foreknown. but prior to this invention, have included going drawing comprises a cupped casing ID to an actuator which contacts directly with and the open end of which is secured a mouth piece positively flexes the diaphragm, the operation of II. The inner end l2 of the casing is closed the actuator being controlled either mechanically and the open end terminates in an outwardly w or electrically. extending flange l3 which corresponds in general The primary object of this invention is to prodimensions to a flange i l formed on the mouth vide an audible signal device including 2. diapiece! I. Spanning the opening l5 of the casing phragm, which diaphragm is vibrated by electrii0 is a diaphragm it which is preferably clamped cal impulses set up and-controlled by an electric between the flange i3 of the casing and the flange circuit. [4 of the mouth piece by bolts or other suitable 15 Another object of this invention is to produce means ll. Thus the diaphragm separates the an audible signal device capable of emitting more casing from the mouth piece and also completely than one tone, the individual tones or components seals the casing ill. thereof being under the operators control. Within the casing Ill are mounted a pair of go A further object of this invention is to produce electro-mechanical systems 0 and the an audible signal'device including 'a howlingsysphragm l6 constituting an element of each. One term which comprises a self oscillating circuitor, of said systems emits the fundamental note of in other words, a closed circuit that reacts upon said diaphragm and the other emits one of the itself and a diaphragm which responds to the harmonic notes due to features which will be set 5 oscillations created by such circuit and-produces forth hereinbelow. The elements and operation a howl. of each-system are similar so that only one need In attaining these and other objects we employ be described in detail, the same reference charan electrical circuit which is tuned substantially acters 'being applied to each. to a natural frequency of the diaphragm and Each system includes a permanent magnet 22 so which includes a source of energy and an oscilsupported within the casing in a predetermined v3O later which varies the flow of energy in the position by any Suitable means, as, for mpl tuned circuit in unison with the vibrations of that described hereinbelow. the diaphragm and with the electrical oscillations Secured in any suitable manner to the ends of the circuit. of the arms 25 of the magnet 22 are blocks 26 Other objects of this-invention will :be apparof soft iron which function as pole pieces for 35 ent from a consideration of the following specithemag'net 22 and project beyond the ends therefication and of the accompanying drawings which of. Rigidly attached to the magnet 22 by feet form a part thereof and in which 21 is a granular carbon transmitter button 28 of Fig. 1 is a plan view of one embodiment of a type well known in the telephone art. The

to this invention the casing and mouth piece being internal construction of this transmitter button 40 in cross section; is no part of the present invention and hence Fig. 2 is a side elevation of such embodiment is not here illustrated and will not be described the casing being in cross section; in detail. It is sufiicient for the present purpose Figs. 3 and 4 are views partly-in cross section to state that it has the characteristics of varyof a detail of such embodiment; ing its electrical resistance in response to small Figs. -5, 6, and '7 are diagrammatic views of variations of pressure applied at the pressure various circuits that might be employed in car- 'head29. Anarmature 3B is rigidly connected to rying out this invention with a structure similar the pressure head 29 of the transmitter button to the embodiment shown in Figs. -1 and 2; 28 and extends across the inner ends of the pole 5,0 Fig. 8 is a view in longitudinal sectionof pieces 26. The armature is held away from the another embodiment of this invention; pole pieces 26 by a spring 3| which thus places Figs. -9 and 10 are cross sectional views taken a normal pressure upon the head 29 of the butalong the lines 53-43 and 10-40 of Fig. 8; ton 28. The mass and resiliency of each arma- .-Fig. 11 is a-view partly in section of'a detail ture 30 and its connections are so proportioned r ofsuch embodimentrand that its natural frequency of vibration is the 55 same as a natural frequency of the diaphragm I6. Across the arms 25 of the magnet 22 is mounted a fixed condenser 32 secured in place by means of screws 33.

Thus two paths are provided in the system through which the magnetic flux will flow between the pole pieces 28, one through the diaphragm l6 and the other through the armature 30. Associated with the armature 30 is a regenerative member, in the present embodiment the transmitter button 28. As previously pointed out one feature of this invention is to provide means for varying the magnetic flux in both paths. One such means will be described below, such description being merely illustrative and not limitative.

The magnetic flux through the body of the magnet 22 is held substantially constant by the nature of the permanent magnet. Wound around each pole piece 26 is a coil 35 by which the flow of the flux through the two alternate paths is influenced and varied. Hence through each path there is a constant component of magnetization due to the permanent nature of the magnet 22 and a variable component due to the coils 35.

Figs. 1 to 4 inclusive disclose the systems 20 and 2| secured in the casing H] by means of a flanged cup 40, the flange M thereof extending between the flanges l3 and I4 and being clamped behind the diaphragm It by the bolts ll. Near the center of the cup 4!! are formed a pair of parallel slots 42, through which the pole pieces 26 extend. The pole pieces are wider than the slots 42 and are provided with notches 43 at the ends of the arms 25, which receive the edges 44 of the slots 42. The cup 43 and the pole pieces 26 when placed in the slots 42 and secured to the arms 25 will thus support the magnets 22 and the other elements of the systems 20, 2|. The coils 35 are separated from the bottom of the cup 40 by suitable insulation !5. Suitable openings through the bottom of the cup 40 are provided to permit the electrical connection of the coils 35 with the other elements of the systems.

In the following description of the electrical connections and operation attention is directed to Fig. 5 the electrical connections having been omitted from Figs. 1 and 2 for the purpose of clarity. In that figure to the various elements dia'- grammatically shown are applied the reference characters previously employed.

The coils 35 are in series, the outer ends being connected by a lead 3i; and the inner ends of the coils being connected by leads 3'1 and 38 to the fixed condenser 32, (see Fig. 5). The condenser 32 is of such capacity that coils 35 and their connections form a tuned circuitthe frequency of which is determined by the condenser 32 to be the same as the pitch of the diaphragm l 8. Thus the tuned circuit and diaphragm I6 constitute an electromechanical system predisposed to oscillate at a natural frequency of the circuit and the diaphragm.

Current is supplied to the tuned circuit from a suitable source of energy such as a battery 50 one pole of which is directly connected to the lead 38 of the tuned circuit by a lead 5! The other pole of the battery is connected to the armature 3!} by a lead 52 which includes any type of make and break switch indicated on Fig. 5 by the numeral 53. The base of the button 28 is connected to the tuned circuit by a lead 54 joining the lead 31. The lead 52 is here shown connected to the negative pole of the battery 50 and the operation of the system 20 will be so described. Upon closing the switch 53 direct current will flow from the battery 59 through the coils 35 and return through the armature 353 and the transmitter buttton 28 to the battery. The current flowing through the coils 35 weakens the attraction between pole pieces 26 and diaphragm I6 and strengthens the attraction between the pole pieces 26 and the armature 3E The pressure of the armature against the transmitter button 28 is thereby lowered with a consequent increase of resistance in the transmitter button and a resulting diminution of current in the circuit. The attraction between the pole pieces 26 and the armature 30 is therefore weakened with the result that the spring 3| is free to exert increased pressure upon the transmitter button, decreasing the resistance of the latter and causing the current to increase again, whereupon the same cycle is repeated as long as the switch remains closed. These variations of attraction, pressure and resistance modulate the current flowing in the circuit at a frequency determined by the resonant frequencies of the armature 3G and the electrical circuit. As previously stated these elements are resonant at the same frequency as diaphragm IS.

A portion of the pulsating current flows through the condenser 32 in the tuned circuit, thus maintaining oscillations at the frequency determined by the condenser 32 which frequency, as previously stated, is the same as that at which the diaphragm l6 and armature 39 are predisposed to oscillate. The diaphragm l6 will thus be actively vibrated and emit a howl or powerful note into the mouth piece H. The pitch of the howl or note is determined by the natural frequency of the tuned circuit through the condenser 32, the diaphragm It and the armature 36 and its spring support 3|.

The electro-mechanical system 2i, while similar in structure, operation and function to the system 253, differs therefrom in that the tuned circuit comprising the coils 35 and the condenser 32 is tuned not to the fundamental frequency of the diaphragm IE but to some other frequency which may be harmonic thereto, and the armature 30 is also predisposed to oscillate at such frequency. Furthermore, the poles 26 are preferably presented to an anti-nodal point of the diaphragm l6 when vibrating at such other frequency. Hence upon closing the switch '53 the diaphragm will emit a howl or note in the same manner that has been described, but at another tone, which may be any pitch harmonic to the note created by the system 26. Both switches may be closed simultaneously thus causing both notes to be emitted by the device and produce a chime effect.

Fig. 6 shows diagrammatically another embodiment of the invention in which a vacuum tube 60 takes the place of the transmitter button and acts regeneratively to maintain oscillations of the electric circuit and hence vibrations of the diaphragm. In this embodiment an A battery 5i is shown for heating the filament or" the vacuum tube 60, and a transformer 52 is shown for coupling the grid of the vacuum tube to the output circuit in a manner well known in the art.

Fig. '7 shows another circuit which could be used and which differs from the circuits shown in Figs. 5 and 6 in that battery 59 and the trans- P total oscillating current passes through the input elements, viz. the battery 50' and the regenerative element 28. The current required-from this source is thereforerelatively large; but the voltage supplied by the input elements at resonance is only that required to overcome the resistance of the circuit; whereas in Figs. -5 and 6 the current is supplied at the total voltage across condenser 32. 7

It should-be observed thatin every one of these embodiments wehave an electro-mechanical-system predisposed to oscillate at a particular frequency and including a regenerative member. The regenerative member is in two cases'a transmitter button and in the other case a vacuum tube upon which the. oscillations of the system react to cause increased variations of energy supplied to the system at the same frequency; but other regenerative members could be substituted for those here shown without impairing the operation of the system.

The coils cooperating with the regenerative member function as an amplifier, i. e., they act to deliver increased pulsating energy to the system in response to the current in the system itself functioning regeneratively as the input circuit to the amplifier.

Figs. 8-12 inclusive disclose a more compact embodiment of this invention which however functions in the manner'previously'described.

This embodiment comprises a cupped iron casing I09 to the open end of which a mouth piece IN is secured by crimping over the edge of. the casing as shown or in any suitable manner. In the casing I00 are mounted two cups I02, I03 spaced apart by two pillars I04 and retained between the back wall of the casing I00 and the mouth piece IIII. The inner cup I02 faces the closed end of the casing I90 and is provided with apertures I95, I06 which receive thimbles I01, I08 for a purpose to be described later. The outer cup I03 is provided with a pair of parallel slots I99, II 0 and a pair of hushed openings III, 'I I2 adapted to accommodate wires leading from the interior of the cup I03 to the space behind it. Through the slots I09, I10 extend two pole pieces H3, H4 having heads H5, H6 of somewhat greater width than the slots to form shoulders which abut against the bottom of the cup I03 as shown in detail in Fig. 11. The inner portions of the pole pieces II 3, II 4 are secured to the poles H1, H8 of a single arcuate magnet I19 by means'ofscrews I20. An arched resilient plate 203 interposed between the ends of the magnet II9 and the under side of the cup I53 serves to draw the pole pieces H3, H4 inwardly and hold the overhanging shoulders thereof firmly against the bottom of the cup I03. An iron block I22 attached to the magnet II9 near its center serves as a magnetic bridge connecting the neutral zone of the magnet to the iron casing I09.

Each of the heads H5, H6 supports a coil I24 connected to other parts of the device 'as described hereafter by wires passing through the bushed openings III and II2 but are omitted in Fig. 8 for the sake of clearness.

Mounted upon the outer face of the cup I92 are transmitter buttons I30, I3I. These buttons are of a well known typeeach comprising achamber I32 filled with granular carbon particles I33 and sealed by a flexible film I34 held over the chamber I32 by a flanged ring I35 threaded externally upon the outer wall of the chamber. Carried by the film I34 in contact with the carbon particles I33 is aplate I33 which is supported on the outer face of the film I34. A second plate I39 is mounted at the base of the chamber I32 also in contact with the carbon particles I33. A pin I40 projecting from the base of the chamber I32 and here indicated as integral therewith extends through the thimbled aperture I05 or I06. The buttons I36, I3! are thus mounted upon the cup I02 and are secured in place by means of set screws I4I, I42 which pass through the thimbles I01, I00 and bear upon the pins I40.

An armature I43 is rigidly supported at one end upon an insulating block I44 which is secured to the outer face of the cup I02 by a screw I45 and to the armature I43 by a screw I46. The armature I43 extends between the transmitter button I30 and the inner end of the pole piece -I I3. The end of the armature I43 near the block I44 is provided with a flange I41 preferably arcuate as shown in Fig. 10 and separated from the wall of thie casing I00 by suitable insulation I48. The other end of the armature I43 is provided with a weight I49 which extends between the inner ends of the pole pieces H3, H4. The armature I43 is of steel or other elastic magnetic material rigidly attached near one end to the block I44. The free end is capable of movements of small extent by flexing and a neck I50 of reduced thickness may be provided near the point of support to increase the flexibility of the armature. Near its free end the armature is connected to the pressure head I38, on the screw I31 which projects from the pressure head, by means of nuts I5l.

A second armature I52 is mounted upon the cup I02 and extends between the transmitter but ton I3I and the inner end of the pole piece H4, The armature I52 is fixed to an insulating block I53 carried by the cup I02 by means of a screw I54 and terminates in an arcuate flange I55 which extends between the block I53 and the Wall of the casing I09 being separated from the latter by suitable insulation I56. The armature I52 like the armature I43 is attached to the screw I31 of the pressure head I 38 of the transmitter button I3I by nuts I51. connections from either transmitter button to the ground on the framework of the instrument, while the screws I46 and I54 by which the armatures I43 and I52 are attached to the insulating blocks I44, I53 act as insulated terminals.

Within the cup I93 are mounted two induction coils I58, I59 for a purpose to be described hereafter and attached to the rear face of magnet I I9 by suitable clamps not shown in the drawings, are twocondensers I00 and IGI.

In the closed end wall of the casing I00 are provided openings I02, I63 within which are secured terminals I64, I65 suitably insulated from the casing I00. A screw I65 is also threaded into a button I61 which. is riveted into the wall of the casing and in electrical contact therewith. The grounded screw I36 and the insulated terminals I64, I65 accommodate the external connections to the device.

Extending across the mouth of the casing I00 is a diaphragm I10 preferably of iron held by a ring "I against the outer edge I12 of the cup I03. A weight I13 may be secured at the center of the diaphragm.

The mouth piece IilI may be flanged at its inner end as at I14 and closed at its outer end by a rubber disc I15 protected by Wire mesh I16. The device may be supported upon a bracket I secured to the casing I by suitable means such as rivets IBI.

The pins I40 form electric The neutral zone of the magnet I I9 communicates with the edge of the diaphragm I1i) through the block I22 and the casing I00. Thus two independent paths of magnetism are provided. One path extends from the block I22 through the magnet H9, the pole H1, the pole piece II3, the air gap between the head H5 of the pole piece I I3, the diaphragm I10, and the casing I00 back to the block I22. The other path extends from the block I22 to the opposite pole H8, pole piece H4, the air gap, diaphragm and back through the casing I00 to the block I22.

Moreover the armature I43 with the short gap through the insulation I48 and the casing I00 constitutes a magnetic path between the inner end of the pole piece H3 and the neutral zone of the magnet H9 similar to the path just described formed by the diaphragm I10 and the casing I00 from the head H5 of the same pole piece H3. In the same way the armature I52 and the casing I00 constitute a magnetic path from the inner end of the pole piece H4 to the neutral zone.

Therefore the poles I I1, I I8 of the magnet H9 act independently and take the place of the two horseshoe magnets 22 in the embodiment previously described For the sake of clearness the electrical connections of the parts which have been described are omitted in Figs. 8, 9, and 10 and are shown diagrammatically in Fig. 12. Referring to the latter it may be seen that when a switch 2% is closed current will flow from a battery so: through the primary winding of the induction coil I58, the armature I43, the transmitter button I30 and the grounded terminal I86 to the opposite terminal of the battery. When the armature I43 vibrates causing fluctuating pressure upon the transmitter button the current in the circuit will fluctuate and an alternating voltage will be induced in the secondary winding of the induction coil I58 causing current to flow in the tuned closed circuit through the secondary winding, the condenser I09 and the coil I24. The resonant frequency of the tuned circuit is an inverse function of the capacitance of the condenser I69 and the inductance of the windings included in the closed circuit. When a low frequency is desired the inductance required with a given condenser is relatively high and the resistance of the coil I24 will ordinarily be high also. When the coil and condenser are connected directly to the battery a high battery voltage is required, corresponding with the high resistance of the coil I24. The function of the induction coil I50 is to step up the alternating component of voltage to a value suitable for a coil of high inductance and resistance when the primary circuit is operated from a source of low voltage and high current capacity.

A switch 202 controls the corresponding parts I59, I52, I3I, ISI, and I24 in the lower portion of the diagram which constitute primary and secondary circuits identical with those which have been described, but adapted for operation at a different frequency which may be one harmonic to the frequency of the upper circuits.

The weights I13 and I49 which are shown in Fig. 8 attached respectively to the diaphragm I10 and the armature I43 are for the purpose of loading these parts for a lower natural frequency of vibration than they would otherwise have.

As previously pointed out in connection with the first embodiment the transmitter button will function as a regenerative member to set up oscillations and cause a vibration of the diaphragm I10 which will emit a howl into the mouth piece II.

The transmitter button I30, armature I43, coil I24 on the pole piece H3 and their connections form an electro-mechanical system tuned to the fundamental frequency of the diaphragm I10, the mass and resiliency of the armature Hi3 and its connections being so proportioned that its natural frequency of vibration is the same as the fundamental frequency of the diaphragm I10.

In the same respect the button I3I, armature I52, coil I24 on the pole piece H4 and their connections form an electro-mechanical system tuned to another frequency which may be one harmonic to the fundamental frequency of the diaphragm I10, the mass and resiliency of the armature I52 and its connections being so proportioned that its natural frequency of vibration is the same as that of the system as a whole.

While certain embodiments have been shown and described, we are not limited thereto since it is obvious that other embodiments of this invention could be made without departing from the spirit and scope of this invention as set forth in the following claims.

Having thus set forth our invention, what we claim is new and for which we desire protection by Letters Patent is:

1. In an audible signal device a permanent magnet, a pole piece extending from a pole thereof and acting upon a diaphragm through one air gap and upon a vibrating armature through a second air gap, a coil surrounding said pole piece so disposed that current acting therein to increase the permanent flux of said magnet at one air gap diminishes the permanent fiux at the other air gap, and an electric circuit including said coil, a source of direct current and a modulator actuated by the vibrating armature, and acting to diminish the current in the electric circuit as the armature is attracted to the pole piece and thereby to maintain current oscillations through the coil and to sustain vibration of said vibrating armature and said diaphragm.

2. In an audible signal device a permanent magnet, a pole piece extending from a pole thereof and acting through one air gap upon a diaphragm resonant at a certain frequency and through a second air gap upon a vibrating armature resonant at the same frequency, a coil surrounding said pole piece so disposed that current acting therein to increase the permanent flux of said magnet at one air gap diminishes the permanent flux at the other air gap, and an electric circuit including said coil, a source of direct current and a modulator actuated by said vibrating armature, and acting to diminish the current in the electric circuit as the armature is attracted to the pole piece and thereby to maintain current oscillations through said coil and to sustain vibration of said vibrating armature and said diaphragm.

3. An audible signal device comprising a casing, cups in said casing, a permanent magnet in said casing between said cups, pole pieces fixed upon the poles of said magnet and projecting through slots in one of said cups, coils on the projecting ends of said pole pieces, a diaphragm adjacent to the outer ends of both pole pieces, two armatures adjacent to the inner ends of said pole pieces respectively, two microphones actuated by said armatures respectively and fixed to the other cup, and oscillating electric. circuits supplied by a source of power including said coil's and said microphone, these elements being so disposed that oscillating currents in the electric circuits on the one hand cause the diaphragm to vibrate and to emit sounds corresponding to the variation of electromagnetic attraction between the pole pieces and the diaphragm, and, on the other hand actuate the microphone in accordance with the variation of electromagnetic attraction between the pole pieces and the armature, thereby sustaining the electric oscillations in the circuit.

4. An audible signal device comprising a sound projector and a microphone mechanically resonant to the same frequency, an oscillating circuit also resonant to said frequency electromagnetically coupled to said projector and said microphone and including said microphone and a source of direct current, said microphone maintaining electric oscillations in said circuit while the sound projector and its electromagnetic coupling translate said oscillations into sound waves.

5. An audible signal device comprising a cupped casing, a diaphragm extending across the mouth of said casing, a permanent magnet, an armature and a modulator actuated by said armature in said casing, a pole piece secured to one pole of said magnet, cooperating at one end with said diaphragm and at the other end with said armature, a coil surrounding said pole piece and an electric circuit including said coil, said modulator, and a source of direct current, said circuit being resonant at a natural frequency of the diaphragm and acting regeneratively to maintain oscillating electric current through the coil and thereby to cause vibrations of said diaphragm.

MAURICE E. PIPKIN'. ELI JUDSON BLAKE. 

